I've never used it, but based on what I have read about it, this language seems fairly radical (well, not completely - LISP could be considered a prototypical f

I've never used it, but based on what I have read about it, this language seems fairly radical (well, not completely - LISP could be considered a prototypical form?): https://www.jetbrains.com/mps/ https://www.jetbrains.com/mps/ It is open-source, too: https://github.com/JetBrains/MPS https://github.com/JetBrains/MPS It seems to have active development, and - interesting aside - it is written in Java. But again - it purports to do what you seem to be explaining here, and a bit more: It's a system that lets the programmer define the programming language as they use that same language, for the specific purpose at hand (aka, DSL - Domain Specific Language). As I've noted - I've not used this tool, but I've kept it in the back of my mind as the concept seems very fascinating to me (I don't know if it is practical, workable, or anything else - but I do think it's a "neat" idea).